Exhibit 5.1

                  Opinion and consent of Clifford Chance US LLP





June 23, 2003




Ligand Pharmaceuticals Incorporated
10275 Science Center Drive
San Diego, California   92121

                  Re:      Ligand Pharmaceuticals Incorporated Registration
                           Statement on Form S-8 for (i) 750,000 Shares of
                           Common Stock and Related Stock Options issuable under
                           the 2002 Stock Incentive Plan, and (ii) 400,000
                           Shares of Common Stock issuable under the 2002
                           Employee Stock Purchase Plan.

Ladies and Gentlemen:

We have acted as counsel to Ligand Pharmaceuticals Incorporated, a Delaware
corporation (the "Company"), in connection with the registration on Form S-8
(the "Registration Statement") under the Securities Act of 1933, as amended of
(i) an additional 750,000 shares of common stock (the "Common Stock") and
related stock options for issuance under the Company's 2002 Stock Incentive
Plan, as amended to date (the "Stock Plan"), and (ii) an additional 400,000
shares of Common Stock under the Company's 2002 Employee Stock Purchase Plan, as
amended to date (the "Employee Plan"). All of such shares of Common Stock are
collectively referred to herein as the "Shares."

This opinion is in accordance with the requirements of Item 8 of Form S-8 and
Item 601(b)(5)(i) of Regulation S-K.

We have reviewed the Company's charter documents and the corporate proceedings
taken by the Company in connection with the establishment and amendment of the
Stock Plan and the Employee Plan. Based on such review, we are of the opinion
that if, as and when the Shares have been issued and sold (and the consideration
therefor received) pursuant to (a) the provisions of option agreements duly
authorized under the Stock Plan and in accordance with the Registration
Statement, or (b) duly authorized direct stock issuances in accordance with the
Stock Plan and the Employee Plan and in accordance with the Registration
Statement, such Shares will be duly authorized, legally issued, fully paid and
nonassessable.

We consent to the filing of this opinion letter as Exhibit 5.1 to the
Registration Statement. In giving this consent, we do not thereby admit that we
are within the category of persons whose consent is required under Section 7 of
the Securities Act of 1933, as amended, or the rules and regulations of the
Securities and Exchange Commission promulgated thereunder, or Item 509 of
Regulation S-K.

This opinion letter is rendered as of the date first written above and we
disclaim any obligation to advise you of facts, circumstances, events or
developments which hereafter may be brought to our attention and which may
alter, affect or modify the opinion expressed herein. Our opinion is expressly
limited to the matters set forth above and we render no opinion, whether by
implication or otherwise, as to any other matters relating to the Company, the
Stock Plan, the Employee Plan or the Shares.

Very truly yours,

/S/CLIFFORD CHANCE US LLP

Clifford Chance US LLP